JP2002338780 discloses a way to improve the dispersibility of a carbon black in a conductive elastomer composition which is prepared by adding the carbon black as a conductive filler to a styrene-ethylene-butylene-styrene block copolymer (SEBS). By adding a carbon black and a maleic-anhydride-modified styrene-ethylene-butylene-styrene block copolymer to an SEBS, the dispersibility of the carbon black in the SEBS is improved.
In US2002/0188078 is disclosed a cable wherein at least one coating layer consists of a recyclable material which is halogen-free and has superior mechanical, electrical, and flame-retardant properties. This material consists of a polymer mixture comprising: (a) a crystalline propylene homopolymer or copolymer; and (b) a copolymer of ethylene with at least one alpha-olefin having from 4 to 12 carbon atoms, and optionally with a diene; the said copolymer (b) being characterized by a density of between 0.90 and 0.86 g/cm3 and by a Composition Distribution Index, defined as the weight percentage of copolymer molecules having an alpha-olefin content within 50% of the average total molar content of alpha-olefin, of greater than 45%. This material may also include a flame-retardant inorganic filler.
In EP1619217 is disclosed an insulation layer for cables comprising a heterophasic polymer composition having superior mechanical and electrical properties and being environmentally friendly. The heterophasic polymer composition comprises a polymer matrix and dispersed therein a propylene copolymer having a weight average particle size of less than 1 μm.
In U.S. Pat. No. 6,663,974 is disclosed that MAH-grafted polypropylene (MAH-g-PP) is used to improve the poor adhesion of polyolefins to metals.
In EP1956611 is disclosed a power and/or telecommunication cable (I) which comprises at least one layer of a material comprising hardened phenolic resin nodules that are dispersed throughout the material, obtained from a composition (II) containing a thermoplastic polymer matrix and a phenolic resin, where the phenolic resin is phenol formaldehyde novolac resin or phenol novolac cyanate ester resin.
In EP1786864 there is disclosed compositions and shaped articles comprising or produced from the compositions. The compositions can comprise (a) at least one polypropylene polymer and (b) at least one E/X/Y copolymer wherein E comprises ethylene; X is a monomer such as vinyl acetate and alkyl (meth)acrylic esters; and Y is one or more additional comonomers such as carbon monoxide; sulfur dioxide; acrylonitrile; maleic anhydride; maleic acid diesters; (meth)acrylic acid, maleic acid, maleic acid monoesters, itaconic acid, fumaric acid, fumaric acid monoester, and salts thereof; glycidyl acrylate, glycidyl methacrylate, and glycidyl vinyl ether in which, based on the E/X/Y copolymer, X is from 0 to 50 weight %, Y is from 0 to 35 weight % of said, X and Y cannot both be 0%, and E is the remainder.
None of the documents however addresses undesired increase in volume resistivity upon ageing at elevated temperatures of solid conductive filler (e.g. carbon black) filled composites.